The present invention relates to well servicing fluids. More specifically, the present invention relates to water-in-oil (invert) emulsions for use in well servicing operations such as work-overs, fracturing, completing, hole abandonment, etc.
Oil based well servicing fluids find particular application in fracturing and packing operations. For example, oil bearing sands of low permeability are commonly subjected to extremely high fluid pressure so as to crack them open, generally along bedding planes, and the fractures so formed are held open by solid propping agents introduced with the fracturing fluid. Such fracturing fluids are desirably oil based having a low filtration loss. Oil based fluids are also commonly used as packer fluids to fill the annular space between the casing and the walls of the hole, the oil based fluids serving to minimize corrosion and provide low fluid loss properties so that the packing fluid remains in place over a long period of time.
Invert emulsion well fluids have been developed to overcome certain deficiencies of simple oil based fluids which have long been utilized in well servicing operations described above. However, such invert emulsions, while overcoming many of the deficiencies of simple oil base fluids, have suffered from certain problems such as for example, the tendency for the oil phase to at least partially separate from the emulsion. Additionally, in many invert emulsion well servicing systems, there arise problems in controlling solids settling.